Hi, I am trying to spec a server for Exchange 2010 running on Server 2008. 1200 users, average mailbox size of 300MB, fairly light users – about 50 messages per day with average message size of 75kb. I am thinking of multi-role server - mailbox, hub transport and client access all on one server in a DAG. I have spent some time reading but getting a little confused with all the info available. I would like some pointers on how to spec the server; will both servers need to be the same spec? Any help would be appreciated.

Always best to have the servers sized the same so any one server can handle the full load. What are you looking to do for storage, DAS, SAN? Have you gone through the Storage Role Calculator yet?

I would start by running the Profile Analyzer ( http://technet.microsoft.com/en-us/library/bb508856(EXCHG.65).aspx ) so that you have a better idea of average message size and send/receive numbers. Once you have those numbers run them into the storage calculator so that you can get an idea of IOPS required and recommendations on DB numbers and LUN sizing and numbers. That will take care of the Mailbox side of things. For sizing the CAS role have a look at the CAS sizing white paper Microsoft provides (http://technet.microsoft.com/en-us/library/ff803560.aspx) but the Mailbox sizing calculator will give you recommended CAS and HT server numbers. DAG configuration and if you need a CAS array will be driven by up time requirements that you have. You should spec the servers the same if you are looking at a 2 server multi role DAG. Just be aware that you will not have high availibility on the CAS unless you implement a load balancer. MS NLB will not work in your situation so I would recommend looking at one of the Kemp load balancers.Matt Cline - MCSE+M, MCITP: EA | EMA (2007, 2010) | Lync 2010 Blog: exchangeadventures.wordpress.com

Many thanks. The profile analyzer helped with the process.